Apparatus for bending glass tubes



A. GREINER APPARATUS FOR BENDING GLASS TUBES Jan, 17, 1950 2Sheets-Sheet 1 Filed April 27, 1944 m in Q I P 1 G n h n d m G HisAttorney Jan. 17, 1950 QQE N 2,494,871

APPARATUS FOR BENDING GLASS TUBES Filed April 27, 1944 2 Sheets-Sheet 2In Ventor:

Alfred Qreinr,

is Actorneg Patented Jan. 17, 1950 UNITED STATES PATENT OFFICE APPARATUSFOR BENDING GLASS TUBES Alfred Greiner, Cleveland .Heights hio, assignorto General Electric Company, a corporation of New York ApplicationApruav, 1944, SerialNo. 534,536

cross-sectional.shape of the tubular glass envelope.

'E'urther objects and advantages of my in 'vention will app ar from thefollowing description .of aspecies. thereof and from the accompanyingdrawing in which: L

Fig. '1 is a diagrammatic side elevation of apparatus comprising myinvention; Fig. 2 is a "transverse section on the line2-2 of Fig. 1;Fig. 3 is. atransverse section on the line 3-3 of Fig. 1; Fig. *4 is afragmentarysection, on the line 4-4 of 'Fig. 3.0'f thefforward end ofthe push :tube and the cc-operating end of the tubular glass elementttobe bent; Fig. 5 is a fragmentary transverse section onthe line 5-5 ofFig. 1 Fig. 6 is a transversesection through the grooved reshaping form,on theline 6.--6 ofFig. 1; Fig. 7 is an enlarged sectional view, on theline 1- -1 of Fig. 1, showing the clamp on the split form for fasteningtheforward end of the glass element thereto; Fig. Bis-a fragmentaryperspective View of the reshaping form showing the manner in-which thefront end of the glass element is clamped to the form; Fig. 9 is a"fragmentary section throughthe reshaping form showing the opposite endportions of the glass elementinposition on said form'duringlthe finalstagesofthe In accordance with the invention, the glass tube ortubularlampto be bentfis first carried through a heating zone whereinthe "glass is heated to the propehplastic condition forbending, afterwhich an end of the heated tube 6 Claims. (01. 49 +7) to thereby permitremoval of the bent glass elementfrom the form.

Referring to the drawings, the apparatus according to the inventioncomprises a horizontally extending guide or slide track [0 having aguideway H in the upper sidethereof Within which a slide block or shoeI2 is slidably mounted. The guide or slide ,track IOis supported on astand or table I3 by a plurality of upstanding support legs or standardsM. A hollow push tube I5 is .rigidly fastened to the slide block l2 asby straps l6,the said tube extending longitudinally of the slide trackII] and forwardly of the slide block. The rear end of the tube [5 isconnected by a flexible conduit H, such as a rubber tube, to a source ofair, or a suitable non-oxidizing or reducing gas such as nitrogen; underpressure. "The use of a reducing gas will prevent oxidation of the-metalparts of a lamp envelope assembly where the tubular glass element to 'bebent is in the form of such a lamp assembly.

The tubular glass element Hi to be bentis horizontally supported abovethe slide track H1 in a position extending longitudinally of the saidtrack. For this purpose, the slide track ['0 is provided with aconcavely grooved roller l9 at its forward end for supporting theforward end of theglass element I8, while the rear end of the glasselement/is supported by the front end of the push tube 15 in a way suchthat the said tube communicates with the hollow interior of the glasselement. In the particular caseillustrated,

bending operation; 'and Fig; 10 is a wiring diagram showing the variouscontrol circuits for the apparatus comprising my invention.

the glass element l8 comprises the glass envelope assembly of a tubularelectron discharge device, such as a fluorescent lamp for instance, the

'said lamp 18 comprising a tubular glass envelope havinga mount2li (Fig.'4) sealed within each end here0f and an exhaust tube 2| extending fromthe rear end thereof. Where the lamp is to be bentinto substantiallyacomplete circle,the

exhaust tube "2| is"laterally offset a sufficient amount to oneside ofthe envelope, at a point closely a'djacentthe rearen'd of the envelopeas showninFig. 4, so as not to interfere with the front end of theenvelope during the final stages of the circular bending operation. Theoffset por- 'tion'22 of the exhaust tube 2| isinserted within theforward end of the push tube l5, which is likewise olfset upwardly ofthelamp axis so as not to interfere with the front end of the lampla'during thefinal stages of the circular bending operation. The offsetexhaust tube portion *22 rests against the wall of the push tube [5 tothereby supportthe rear end of thelamp l8.

Asshown inFig s. 3 and 4, the forward end of the push tube I5 isprovided with a hold-down shoe '23 overlying the rear end of the lamp H3and having Wing portions 24 curved on their underside to conform to thecurvature of and engage the wall of the lamp. The wings 24 may be linedwith asbestos at least on their under or bulb engaging side, asindicated at 25 in Fig. 3. The rear ends of the wings 24 are formed withdepending lips or lugs 26 which overhang and engage the rear end of thelamp Is to thereby transmit the forward pushing movement of the pushtube IE to the lamp. To permit insertion of the offset portion 22 of thelamp exhaust tube 2| into the push tube l5, the said tube |5, as well asthe hold-down shoe 23, are slotted on their underside, as indicated at21 and 28 respectively.

After the lamp It has been mounted in position on the support roller Hiand push tube i5, the latter is moved forward at a relative slow anduniform rate to thereby advance or push the lamp through a heating zonepreferably provided b an oven or furnace 29, such as an electricfurnace. The movement of the push tube |5 is preferably mechanicallyimparted thereto by suitable means,

, 35 and 36 mounted, respectively, on the said shaft 33 and on a maindrive shaft 31. The main drive shaft 3! is driven by an electricmotor-speed reducer unit 38, mounted on the table I3. through achain-belt 39 connecting sprockets 40, 4| on the main drive shaft 31 andspeed reducer shaft 42, respectively. The drive for the lamp-advancingchain belt 30 is so designed so as to slide the block I2 forwardly inits guideway II, and thus cause the push tube IE to advance the lamp l8through the oven 29 at a uniform and relatively slow rate of about 2feet or so per minute, for

instance.

The electric furnace or oven 29 is normally heated to a temperature justbelow the softening point of the glass of which the lamp I8 is made.Thus, in the case of a soft lead-glass lamp envelope, the oven isnormally heated to a temperature of around 800 C. or thereabouts.

After the lamp H; has advanced a predetermined distance into the oven29, a relay 43 (Fig. is actuated to shunt out a resistance 44 normallyconnected in series with the oven resistan ceheating element 45. Thisproduces increased current flow through the oven heating element 45resulting in increased heating effect therefrom which thus compensatesfor the absorption of heat by the lamp, as it passes through the oven,and therefore maintains the oven at a substan tially even temperature.As shown in Fig. 10, the relay 43, when energized. closes a switch 4-6thereby completing a shunt circuit 41 around the resistance 44. Therelay 43 is connected by leads 48. 49. 50, and through a microswitch 5|,to a suitable source of current supply. The microswitch 5! is controlledby a rotatable cam 52 having an arcuate switch-engaging segment 53 forclosing the microswitch 5|. The cam 52 is mounted on a shaft 54supported on the table l3, and is rotated at a given speed by a chainbelt 55 connecting a. sprocket 56 on the cam shaft 54 with a sprocket5'! on the main drive shaft 31. After the completion of the lamp bendingoperation, the cam segment 53 disengages the microswitch 5| to therebybreak the circuit through the relay 43 and thus permit thte switch 4-6to open and break the shunt circuit 41 across the resistance 44, thusrestoring the oven heating-element circuit 58 to its 5 originalcondition wherein the resistance 44 is connected in series with theheating element 45.

The passage of the lamp |8 through the oven 29 serves to progressivelypreheat the advancing lamp to a temperature just below the softeningpoint of the glass of which the lamp envelope is made. Upon emergingfrom the oven 29, the lamp i8 passes through a supplementary heatingzone wherein the glass lamp envelope is locally heated to its softeningpoint just prior to the bending or reshaping of the same. Such localizedsupplementary heating is preferably provided by means of one or more(preferably two) gas burners 59 directed against the under side or halfof the tubular lamp envelope, in conjunction with an electricresistance-heating shoe 60 overlying the lamp and mounted on the frontend of the oven 29. As shown in Fig. 6, the underside 6| of the electricheating shoe 60 is of concave shape conforming to the cross-section ofthe lamp envelope, and it encloses substantially the entire upper halfsection of the said envelope. The degree of localized heating of thelamp l8 by the gas burners 59 and electric shoe 60 is adjusted to givethe desired temperatures of the upper and lower half sections of thelamp envelope. Preferably, however, considerably more heat is applied bthe electric shoe 60 to the upper side or half of the lamp than isapplied to the lower side by the burners 59, for the reason that most ofthe stretching of the glass, during the bending operation, takes placeat the upper or outer side of the lamp.

As soon as the front end of the advancing lamp |8 emerges fromunderneath the electric shoe 6!), it is clamped to the periphery of aslowly rotating re-shaping form or drum 62 (as shown in Fig. 8) by meansof a clamp 63 on said form, the rear end of the lamp still beingsupported on the roller I9. The electric shoe 50 extends over the top ofthe reshaping form 62 to a point directly above the axis of rotation ofthe form (Fig. .1) so that the upper side of the lamp is heated right upto the moment when the bending of the lamp be ins.

The re-shaping form 52 is mounted on the horizontal main drive shaft 31which extends transversely of the advancing lamp. I8 and is journalledin a bearing 64 on an upstanding bracket 65 fastened to the table l3.The rotative speed of the form 62 is such that its peripheral surfacespeed corresponds to the speed of 55 the linear advancing movement ofthe lamp Ill. The periphery of the form 62 is provided with an annulargroove 66 lined with asbestos 51 and conforming in cross-section to, andaligned with, the lamp envelope so as to partially accommodate theenvelope therein. In the particular case illustrated wherein the lamp I9is of circular cross-section, the peripheral groove 66 is ofsubstantially full semicircular cross-section so as to accommodateapproximately one-half (i e. the under half) of the cross-sectionalperiphery of the lamp envelope.

To permit removal of the bent lamp l8 from the winding form 62 where thelamp is to be bent into an arc of .more than 180, the said form 52 issplit or divided into two disc-shaped halves or sections 68, 69 normallyheld in faceto-face abutting relation but axially separable from eachother along a parting line defining a vertical plane passing through thecenter vline of the semi-circular lamp receiving groove 66 accurate-1Wl'iifiiiS formed whemthe two discs are in" face-- te -face engagement.The discs 63; fil maytbe made of" any suitable material; for; instance,pressed asbestos: One of said'dises, i. e; disefill; is axiallyfixed-,it being screwed or otherwise fastened tb a: flanged collar which is= l:eyed or otiierwise locked to the main drive: shaft: 3-7. The other"disc Bo is axially-displaceable away from tlie fi'xed dise 68; itlbeingscrewed or otherwise=fastened+ to a flanged shaft or pin '1"! 1 which isjournalled in a bearing12 onanupstanding bracket 1%: fastened to thetable Iii. A com pression coil spring T4; interposed between: andbearihg= against thebearing l2 and the flange IE-omthmshaft -I'l5normally maintains the disc H 9 frictional face to-face engagement: withthe other axially-fixed di'scwi The shaft: I -l ex tends through thedisc 69 and: projects; short di'stance beyond the inner face thereofgiasindicartedat' L The said projecting shaft portion 16 is rounded at itsinner end anclfits snugly into-acentral opening 11* in the axially-fixeddisc fifi when' thetwo' discs are in abuttingxen gagement; totherebyinsure proper" alignment er -centering of the engaged discs. At:its outer end, theesliaft Tl is provided with a suitablehand-leor'finger: grip' T8 for pulling the shaft '1 l and attaehed disc-6'9 outwardly tb thereby axially separatetl'ie said disc'from the otherdisc 52.

The clamp-Shier holding the front end of 'the lamn lB withinthegroovefib in the winding form 625 comprises a lever ill? (Figs. '7) pivot'all3mounted' ona ring=8ll=rotatable within agroove 8 l' in tlie=periplieryof the flange BEoncollar 10 The'lever 19-2 is: pivotally mounted on asmall block:83 fastenedtothe ring 80, and the rotatability of theringrelative tothedise fifl per mits the*adjustinentof the clamp '63 toany angular-position aroundtlie re shaping form fl'z One arm 8MoftheleVer'"l9iextends across-the annu- 1ar groove-66 of the-closed "-form6 2 and is-curved to conform'to and'enga-ge the exposed or outerhalf-portion of 'the cross sectional periphely of the-lampwithin'the'said'r groove 5%.- The i curved or-arcuateflammengaging arm84 0f the clamp lever1B is-preferablycovered with asbestosor otherheat-insulating material, as indicated at 85': The otherarmflfi -of'theclamp lever N ls formed as a liandlefor operating the clamp. A

compressioncoil spring 81, interposed between 5 and bearing against thelever arm as and the lever supportfiblock 83,- normally maintains theolampleven'w in its closed or lamp-clamping position, as shown in Fig;7;

fit about the same" time the front end of the 8 advancing lamp 18 isclamped to the reshaping form:62 'by=thec1amp63; a suitablenon-oxidizinggas such as nitrogen, under relatively lowpressure,is-introduced into the heated lampto prevent collapsing" ofthe-softened glass wall thereof: As shown in Eig. 10; the gas supply forsuch purpose is: produced by the opening or a solenoideaetuatedr valve881 in the gas: line {in which: isaconnectedi to the pushtube: [5 byfliexibleiconduiti or tube H. A! sufficient amountof?thegasriflowing:through the push tube 1 Ethan enters the; lampexhaust. tube Zil andflows: into the lamp? to time prevent. thecollapsing of the softened wall: of? the lamp. The gas passing throughthe tube I5 may be at a pressure of l 1% to-2iinchesrhead*of water, forinstance:

'Ilhe flow-ofl gas-rthrough thepush tube Wand into i theflampw IB'iis*automaticallyturned' on just before: the: start: oil lamp bending andcontinues until? the bending: operation is completed; when iii) it' -isautomatically? turned: offz; Eon thisrtpure pose, the solenoid ofthevahreltlfl in thecgasrsupa plyvlinezflthis connected to a sourceof:current supply: through; aimicrosw-itch- 9th whichiais con:- trolledlbyaiseementval;1on:thercam:52:. The cam segmentmd iC1OSBS"thBLPSWlZtChL atthe proper instanti-to: complete the circuit through i the sole+ mold"of theavalve' flfitand: thus openwtheclatter to permit the fiow of gas:through the gas 1inei89 andipushltnbe [Shand -thence into the lam-p18:Upon completion: of'rthealampr bending operation; the: camnsegment: 91:disengages the switch;- 89; allowing; the latt'erl to open" andthus:break: the circuit": through the solenoid? or the valve: 88 whiohcthencloses to shutrofl the-gasrfiow in the gasaliner8-9:

After' the clamping; of the front end; of: the heatedlamp-to the :form-62;: the l continued: slow rotationof the latter-r causes the softened:lamp to be progressivelywdrawn' and: bent aroundithe form; the bendingforce being providediby the weight: of the-rear portion; of theadvancingzlamp which: has not as :yetireached thecreshapingiform.Duringthefinalistageswor the" bending operation,

F however; very' little of: the lengthx of theela-mp remains to providethe: bending I forceanecessary to urge or bend" the rear end; of thelamprdbwn into-the groove fifiainwthe reshaping 15017111162? Totherefore provide the necessary bending force to: insure thecontinuedand? proper bending of the lamp right to the veryend thereof; the pushtube l6 may: be lightly" pressed down during the fi'nal' stages of thebending operation sa es: to cause the hold-down shoe 23*to pressd'own'on therear'end of the lamp andthus continuously urge the rearportions of "the lamp down into the groove fi'fiin the reshaping form62. Thedown- Wardpressureomthe push tube l5 rnay be manually appliedthereto; orit may be applied thereto by suitable guide meanssuch as' aroller ")3 engaging with the upper side of the push tube to preventany-upwardspringing of theunsupported; forward end-portion of the pushtube which otherwise may occur.

Upon-completion of the bending operation, the electric motor of themotorrreducer unit 38 is automatically turned off by the opening of amicroswitch 92 in the motor circuit, the said ,switchlbeingcontrolled bya segment 93' on the cam 52 which segment disenga es the. switch 92, atthecompletion of the bendingcycle, to thereby permitwthe said switch toopenand. thus interrupt themmotor. circuit. Likewisevthe gas, firesjmmithe burners 53. are preferably shut ofifl, auto.-

matically upon completiontof the bending operation, by. the closing.ofsolenoid+aetuated valves 94-.located in the-gasl-andair lines=95and96,- re.- spectively, for the burners. The closing of; the

z-ValV8&- $14-: isenacted by the opening of amicro- 'heatedibyuthe gasfires from the burners 59v.

Whem the sform 612:; withthe lamp wrapped therearnund; has stopped its;rotational" move:- ment: theraxia-lly movablehalf-section 59 lof theform. is separatedz from the other axially-fixed half: GBtthereofrandzth 1 Temp 1 themremoved {from the form through the space between theseparated form half --sections.

Following each bending cycle, the apparatus is re-set to proper startingposition preparatory to the start of the next lamp bending operation.This is done by first disengaging the drive between the sprocket 35 andits support shaft 33, then running the motor 38 by closing a hand switch99 in the motor circuit until the cam 52 has completed its fullrevolution and is again in its original starting position, and finallywithdrawing the push tube and the associated slide block 12 to theiroriginal starting position while maintaining the disengagement of thedrive between sprocket 35 and shaft 33. As shown in Fig. 5, the drivebetween the sprocket and its support shaft 33 is through a drive pin orkey I00 which interconnects and rotatively locks the said sprocket witha flanged collar it! keyed or otherwise fastened on the shaft 33. Thedrive pin I00 projects through and is slidably mounted within thesprocket 35 which is freely rotatable on the shaft 33. The flangedportion of the collar IOI is provided with an annularly arranged seriesof holes or recesses I02 into any one of which the pin I00 is insertableto rotatively interlock the sprocket 35 and collar NH. The disengagementof the drive between the sprocket 35 and its support shaft 33 iseffected by simply withdrawing the pin I 00 from its co-operating recessI02 in the collar IUI.

After the lamps l8 have been bent into circular shape in the mannerdescribed hereinabove, they are subsequently exhausted, filled with gas,sealed-oil, and finally based all in the conventional manner, therebycompleting their manufacture. The base with which the lamp is providedmay be of any suitable type, such as that shown, for instance, in U. S.Patent No. 2,339,166 to W. Harrison, issued January 11, 1944.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. Apparatus for bending tubular glass elements comprising, meansproviding a heating zone, means adjacent the heating-zone to support andadvance the glass element through said heating zone, a drum-shaped formdisposed adjacent the path of travel of the heated glass element andadapted to receive the element in tangential relationship, said formhaving a peripheral groove for receiving the element therein, grippingmeans on said form for attaching an end of the heated glass element tothe form and within the groove therein, and support means comprising apair of aligned support shafts rotatably mounting said form for rotationabout its axis to thereby cause the heated glass element to be bentaround the form within the groove therein, said form being divided intotwo disc-shaped sections each mounted on a respective one of saidsupport shafts and being axially separable on their support shafts atsaid groove to provide an unobstructed space therebetween for removal ofthe bent glass element from said form by movement thereof through thesaid space.

2. Apparatus for bending tubular glass elements comprising, meansproviding a heating zone, means adjacent the heating zone to support andadvance the glass element through said heating zone, a drum-shaped formdisposed ad- 7 jacent the path of travel of the heated glass element andadapted to receive the element in tangential relationship, said formhaving a peripheral groove for receiving the element therein, grippingmeans on said form for attaching an end of the heated glass elementtothe form and within the groove therein, support means comprising a pairof aligned support shafts rotatably mounting said form for rotationabout its axis to thereby cause the heated glass element to be bentaround the form within the groove therein, said form being divided intotwo disc-shaped sections each mounted on a respective one of saidsupport shafts and being axially separable at said groove to provide anunobstructed space therebetween for removal of the bent glass elementfrom said form by movement thereof through the said space, and meanscomprising a gaseous pressure supply adapted to be connected to theinterior of the glass element for maintaining the atmosphere within saidelement at a sufiicient pressure during the bending of the element toprevent collapsing of the softened wall thereof.

3. Apparatus for bending tubular glass elements comprising, meansproviding a heating zone, means adjacent the heating zone to support andadvance the glass element longitudinally thereof through said heatingzone, a rotatable drum-shaped form disposed adjacent the path of travelof the heated glass elements and adapted to receive the element intangential relationship, said form having a peripheral groove forreceiving the element therein, gripping means on said form for attachingthe front end of the advancing heated element tangentially to the formand within the groove therein, support means comprising a pair ofaligned support shafts rotatably mounting said form for rotation aboutits axis to thereby draw and bend the heated element around the formwithin the groove therein, said form being divided into two disc-shapedsections axially separable at said groove and each mounted on arespective one of said support shafts, said shafts and associated discsbeing axially movable apart to provide an unobstructed spacetherebetween for removal of the bent glass element from said form bymovement thereof through the said space, and means comprising a gaseouspressure supply adapted to be connected to the interior of the glasselement for maintaining the atmosphere within said element at asufficient pressure during the bending of the element to preventcollapsing of the softened wall thereof.

4. Apparatus for bending into circular shape a tubular lamp envelopeassembly having a laterally-offset open exhaust tube, said apparatuscomprising an oven, carrier means adjacent the oven to support andlinearly advance said envelope through said oven, said carrier meansincluding a push tube offset laterally of said envelope and adapted toreceive the said exhaust tube, supplementary heating means locatedadjacent the path of travel of the glass element from the oven forprogressively heating the advancing envelope to the softening pointthereof, a drum-shaped form disposed adjacent the path of travel of thesoftened envelope and adapted to receive the envelope in tangentialrelationship, said form having a peripheral groove for receiving theenvelope therein, gripping means on said form for attaching the frontend of the advancing softened envelope to the form and within the groovetherein, means rotatably mounting said form for rotation about its axisto thereby draw and bend the softened envelope around the form withinthe groove therein, and means comprising a gaseous pressure sourceadapted to be connected to the push tube for creating a flow of gasthrough said push tube to cause introduction of the gas into theenvelope through the open exhaust tube thereof to thereby preventcollapsing of the softened envelope wall.

5. In apparatus of the class described for bending glass tubes intoarcuate shape, a peripherally grooved forming drum comprising twosections axially separable through the groove and mounted on separatesupport members arranged to be moved apart for removal of the bent tubefrom the drum.

6. In apparatus of the class described for bending glass tubes intoarcuate shape, a peripherally grooved forming drum comprising twosections axially separable through the groove and mounted on separatesupport members arranged to be moved apart for removal of the bent tubefrom the drum, and spring means normally holding said sections together.

ALFRED GRE'INER.

10 REFERENCES CITED The following references are of record in the fileof this patent:

UNITED STATES PATENTS Number Name Date 735,307 Smith Aug. 4, 19031,662,428 Lowe Mar. 13, 1923 2,030,399 Pirani et a1 May 13, 1937 102,135,775 Walker Nov. 3, 1933 2,177,743 Pfaff Oct. 31, 1939 2,203,953Brown et a1 July 23, 1940

